<html>
  <head>
    <title>OK</title>
  </head>
<body>
Basic html test.
</body>
<script>
function createFavicon() {
    const link = document.createElement('link');
    link.rel = 'icon';
    link.href = 'favicon.png';
    document.head.appendChild(link);
}
window.addEventListener('message', () => {
    createFavicon();
});
</script>
</html>
